An optical fiber ribbon is a well known structure which includes a plurality of individual optical fibers which are held in spaced positions parallel to each other in a common plane. For example, a typical optical fiber ribbon may include twelve (12) individual optical fiber waveguides aligned relative to one another in a common plane with all of the optical fiber waveguides being imbedded in a single or multi-layer coating of a matrix material, such as a polyurethane acrylate resin.
Each of the individual optical fibers may be provided with a layer of a colorant material to uniquely identify each of the optical fiber waveguides within the optical fiber ribbon. The individual optical fibers may be of various types, including single coated or multicoated optical fibers.
An advantage of using an optical fiber ribbon of the above-described type is that the optical fiber ribbon provides a modular design which simplifies the construction, installation and maintenance of optical fiber cable by eliminating the need to handle individual fibers. For example, the splicing and connection of the individual optical fibers in a ribbon is accomplished by splicing and connecting the much larger ribbon.
While the accessing of fibers in groups of twelve is adequate for splicing a large number of fibers at a location, it is also well known in optical fiber network architectures, such as a fiber in the loop (FITL) architecture, that smaller groups of fibers are often dropped off at a node. Traditional ribbon structures do not easily allow for such entry into the ribbon. There also exists the need to access each individual optical fiber within a ribbon for certain ribbon applications.
In cleanly separating twelve (12) individual fibers from a ribbon structure, the goal is to break the bond between the fibers and the encapsulant resin material. It is well known to use tensile forces to remove the matrix material from a ribbon; however, it is also known that due to the thickness and strength of the matrix material, random fractures may occur in the optical fibers, and unsatisfactory matrix material removal may occur due to such tensile forces. It is also known to cut the ribbon with a knife or pin locally to reduce the encapsulant strength and allow for easier separation by tensile loads. However, hazards with this technique include damaging the fiber coating during blade insertion and during propagation of the split with the blade. Tools have been developed to provide improved blade control to minimize the chance of damaging the individual optical fibers; however, damage may still result if tight position control is not achieved and maintained.
Tensile forces along the longitudinal axis of the ribbon can be produced by pulling, peeling or shaving the encapsulant off of the ribbon. Shaving suffers from the same problems associated with using a blade or pin for cutting. Peeling the encapsulant without the use of a blade may be a good solution, particularly in ribbons using encapsulants strong enough to remain in one piece. However, initiating a peel location may be difficult and also pulling on the encapsulant material in the longitudinal axis is difficult while trying to initiate the peel and hold the encapsulant. It is also known to apply shear forces to fatigue the matrix material. However, this method does not always provide satisfactory results. With all of the methods which involve applying a tensile or shear force to a ribbon, damage may result to the individual optical fibers if the bond between the matrixing material and the optical fibers is sufficiently strong that excess force has to be applied to initiate the peeling and removal of the matrix material.
It is also known to use cyanoacrylate ester adhesives to initiate midspan removal of the matrix material because of the strong bond of the cyanoacrylate with the matrix material. It is also known to use adhesive tape to continue matrix material removal initiated by the use of cyanoacrylate.
To make the use of optical fiber ribbon economically viable, midspan access of individual fibers within a ribbon structure must be feasible with a fast, low-risk method. Additionally, the ability to break off or route smaller groups of fibers from the larger group is desirable. The matrix material removal and breaking off of groups of fibers must be able to be performed in a ribbon with live fibers such that all fiber coatings remain structurally intact after the matrix material is removed. It is also important to retain fiber identification through no degradation of the colored ink coatings on individual optical fibers.